[Study on constructing the U-shaped response relationship of urinary iodine level and thyroid nodule prevalence based...

Area of Science:

• Endocrinology
• Public Health
• Epidemiology

Background:

• Urinary iodine levels reflect recent iodine intake.
• Thyroid nodules are a common endocrine disorder.
• The relationship between iodine intake and thyroid nodule prevalence is complex.

Purpose of the Study:

• To investigate the dose-response relationship between urinary iodine levels and thyroid nodule prevalence.
• To establish an asymmetric U-shaped response curve.
• To estimate the prevalence of thyroid nodules in Chinese residents based on urinary iodine levels.

Main Methods:

• Systematic literature search (2000-2019) in multiple databases using Chinese and English keywords.
• Inclusion of 46 studies (24 domestic, 22 foreign).
• Application of quantile regression and Sigmoid function models to fit the dose-response relationship.

Main Results:

• An asymmetric U-shaped relationship was observed between urinary iodine levels and thyroid nodule prevalence.
• The median urinary iodine level at the piecewise function's cut-off point was 198 μg/L.
• The overall prevalence of thyroid nodules in Chinese residents was estimated at 23.0% (95% CI: 17.3%-30.7%).

Conclusions:

• The asymmetric U-shaped model effectively describes the relationship between urinary iodine and thyroid nodule prevalence.
• This finding suggests that both iodine deficiency and excess iodine intake may increase thyroid nodule risk.
• The study provides valuable insights for public health strategies regarding iodine intake and thyroid health.